What is MTDS in Water Purifiers? Everything you Need to Know

If you are looking for RO water purifier, then you would have come across term MTDS. It is a device used in some of the Eureka Forbes water purifiers such as Aquaguard, Aquasure and Dr. Aquaguard.

THere are plenty of terms used in water purifiers that can be confusing such as MTDS, TDS controller, Taste adjuster. Don’t worry, we will clear all you doubts regarding these terms in this post.

We will discuss everything you need to know about MTDS controller and similar terms, so that you can make an informed buying decision.

For you to understand MTDS, it is necessary to understand what is TDS first.

What is TDS and Why is it Important?

TDS stands for Total Dissolved Solids. It refers to any kind of impurities found in water. It can be organic or inorganic. Inorganic impurities consist of dissolved calcium, magnesium, potassium, sodium, chlorides, bicarbonates, sulfates, toxins and so on, while organic impurities are typically of biological origin.

Water with high level of TDS is unfit for drinking because the impurities can be harmful for health. On the other hand, very low level of TDS means that the water is devoid of essential trace elements such as calcium, magnesium etc. which can be detrimental for health in the long run. This means that, very low as well as very high levels of TDS are not good for health. This is where MTDS controller comes in handy.

What is MTDS in Water Purifier?

MTDS controller stands for Manual TDS controller (or Manual Total Dissolved Salts controller). It is a device that controls / regulates the TDS of output water from an RO water purifier.


As discussed above, very high or very low TDS is not good for health. Hence, RO water purifiers from Eureka Forbes comes with a TDS controller which they have branded as MTDS controller.

Concept of a TDS controller is nothing new and it is present in almost all decent RO water purifiers in India. This is because Reverse Osmosis process is one of the most powerful water purification methods. It not only removes harmful impurities, but also removes essential salts and minerals from water, which creates a need for a TDS regulator.

MTDS controller is a small device that is usually placed inside the water purifier and consists of TDS screw to regulate the TDS of water. You can control the TDS by manually rotating the screw in either clockwise or anti-clockwise direction. Hence, the name manual TDS controller.

Usually, rotating the screw clockwise increases and TDS, while anticlockwise motion decreases the TDS of water.

Most acceptable level of TDS is between 100 and 300 PPM. You can check the TDS of water with the help of a TDS controller or you can ask the service technician to adjust the TDS during installation.

How MTDS Works?

The working of an MTDS controller is quite interesting and simple. To understand its working, let us first understand how an RO water purifier with MTDS works.

Below is the diagram explaining the working of MTDS controller.

How MTDS works

As you can see, water into the MTDS controller comes from two sources. First is RO purified water with ultra-low TDS. The other input if from UF (or MF) purified water. This is done because UF / MF do not remove essential salts and minerals from water unlike RO. This means that the TDS level of this water is high. When water from both the sources gets merged in the MTDS controller, the amount of high TDS water from UF / MF determines the overall TDS of water.

Basically, the TDS screw controls the amount of UF / MF water that is being mixed with RO water. More UF / MF purified water you mix, higher the overall TDS of water. Therefore, clockwise rotation of MTDS controller reduces the flow of high TDS, UF / MF water, which makes the overall TDS of output water lower. Similarly, of you rotate the MTDS controller anticlockwise, it increases the flow of UF / MF water, which increases the overall TDS of water.

Advantages of MTDS in Water Purifier

  • MTDS regulator removes the biggest disadvantage of RO water purification for home use. It adds back the essential salts and minerals back into the water that are removed by the RO method. Hence it makes water healthy for drinking.
  • MTDS is also sometimes called taste adjuster. This is because TDS levels in water are responsible for taste of water. RO water without MTDS can taste bitter or ‘not normal’ because it lacks natural substances. Hence, by regulating TDS of water, MTDS adjusts the taste of water to make it more ‘natural’ tasting.
  • MTDS controller also improves the pH of the water, which is important for our body.
  • This device is easy to use as the TDS screw can be rotated easily by hand (in most of the MTDS controllers). You can keep adjusting the screw until the desired TDS level is reached.
  • It is long lasting device that does not need maintenance. We have come across very few instances where customers faced maintenance issues with the device. Since it is a simple device, it lasts long. Also, it is quite cheap and can be replaced in a cost-effective manner.

Disadvantages of MTDS in Water Purifier

  • MTDS controllers are excellent devices to regulate TDS, but it is ineffective in removing toxic heavy metals such as nickel, cadmium, mercury, lead, arsenic etc. Hence, if your water supply contains heavy metals, then MTDS regulator will not work. This is because the heavy metals are removes by RO water, but the UF / MF water added to this RO water contains heavy metals that are added back.
  • This device is usually placed inside the water purifier encasing. Hence, it can be difficult to access the controller if you are a first timer. Usually, the installation technician will adjust the TDS during the installation of the water purifier. However, if you want to change the TDS levels later it will require some effort.
  • Another disadvantage of MTDS is that it does not come with a TDS meter. This means that you will have to use an external TDS meter to measure the TDS levels so that you can adjust these levels based on your preference.

Frequently Asked Questions (FAQs)- MTDS

Can I buy RO water purifier without MTDS?

If you are buying an RO water purifier, then you should almost always go for an RO with MTDS. Since RO removes more than 90% of the TDS, it is important to have an MTDS regulator so that ‘healthy’ level of TDS can be maintained. Only case when you should avoid an MTDS is when there are heavy metals in the water. In this case, you should go for water purifier with mineralizer.

What is the difference between MTDS and TDS Controller?

MTDS controller and TDS controller are similar in working and usage. ‘MTDS’ term is preferred by Eureka Forbes water purifiers, while TDS Controller is preferred by Kent and other water purifiers.

Is taste adjuster same as MTDS?

Taste adjuster and MTDS are usually the same thing. Since TDS levels in water determine the taste of water, MTDS is also sometimes called taste adjuster.

When should I buy water purifier with MTDS?

You should go for RO water purifier with MTDS if the TDS level of your water is more than 300 – 500 PPM. If it is less than this level, then you can purchase a UV water purifier as well.

Why UV water purifier does not have MTDS?

Since UV water purifiers are meant for purification of water with low TDS of less than 300 – 500, there is no need to regulate the TDS of water. Hence these water purifiers do not come with MTDS controllers.


MTDS regulator is an important device that controls the TDS level of water. This is important for healthy metabolism. These are also called TDS controllers by most of the water purifier brands and all good water purifier brands offer RO water purifier with TDS controllers.

Having a regulator like this also improves the taste and pH of water. Hence, you should never purchase an RO without MTDS, because it can be unhealthy for your body.

The MTDS is quite inexpensive and can be set by hand or a screwdriver. Once you have set the TDS, you may want to check the TDS levels again after 6 to 12 months. Also, for low TDS water, there is no need to go for this device.


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